1. Field
The present invention relates generally to improvements in engine emissions control systems and more particularly pertains to the reduction of engine emissions in automobiles using secondary air injection to aid a vehicle catalyst system during warm-up.
2. Description of the Related Art
Automobiles and other vehicles commonly incorporate an internal combustion engine for providing power to operate their various functions. An unfortunate side effect of the power producing capability of internal combustion engines is the production of exhaust gases containing a variety of harmful or toxic elements. After combustion of an air/fuel mixture in the cylinders of the engine during the power stroke, unspent fuel in the air/fuel mixture is passed out of the engine cylinders and commonly flowed along an exhaust pipe of the automobile. This waste or exhaust gas is then expelled from the exhaust pipe and away from the vehicle into the surrounding environment. These exhaust gases are known to cause a variety of dangerous ailments if inhaled in significant quantities by humans or other mammals and the proliferation of automobiles as the most prevalent means of transportation has made such engine emissions of particular concern. In an effort to help reduce the toxicity of these exhaust gases before their delivery into the environment surrounding the vehicle, emissions control systems aboard these vehicles have been developed in an attempt to eliminate harmful particulates from the exhaust gas via chemical processes before the exhaust gas is permitted to exit the exhaust pipe.
Typically, automobile manufacturers will incorporate a catalyst device as part of the emissions control system through which the exhaust gas is flowed at some location along the exhaust pipe. In order to operate most efficiently at removing the harmful or toxic components of the exhaust gas, the catalyst must be warmed up to a sufficient temperature, oftentimes higher than it normally would exist under ambient conditions. This warm-up is particularly important upon a cold start of the engine and has been accomplished through secondary air injection by incorporating additional external air pumps and associated valves/plumbing onto the vehicle. Such a system directs excess air into the exhaust pipe upstream of the catalyst for aiding in the immediate warm-up of the catalyst, such as during initial vehicle turn-on when the engine is at idle and when there exists a more limited amount of exhaust gas flowing through the exhaust pipe from the internal combustion engine.
However, the reliance upon secondary air injection systems utilizing external air pumps and plumbing increases the cost and complexity of an automobile's power train design. Not only do the additional components add to the overall engineering design cost of an automobile, but also increase the manufacturing cost of every vehicle constructed. Moreover, the addition of supplementary mechanical components onto the vehicle increases the potential for malfunction and adds to the number of parts that may require servicing or repair by an owner of the vehicle. External pumps pose durability issues and may have difficulty surviving the environmental elements encountered by many automobiles, for example, by freezing up in cold or icy temperatures. Furthermore, certain U.S. states require owners to have their vehicles regularly “smog” checked to ensure that the emissions control systems onboard those vehicles are operating effectively in conformance with predetermined environment standards. Particularly in the current environmental climate where an increased emphasis is placed upon clean power generation and the reduction of toxic engine by-products, a system for reducing engine emissions without the reliability problems outlined above is even more desirable.